1. Field of the Invention
The present invention relates generally to oil-flooded screw compressors and also to technologies for avoiding increase in loads on electric motors and power supply circuitry used to drive the compressors.
2. Description of the Related Art
An oil-flooded screw compressor includes therein multiple enclosed spaces, called working chambers or compression cavities, which are formed by meshing the groove of two counter rotors and reducing the spaces between the rotors and the casing that houses the rotors.
While the two meshed counter rotors rotate, each working chamber moves inside the casing, alternating expansion and shrinkage in its volume. Depending on a position of rotors inside the casing, each working chamber communicates with the outside via an opening of the casing or is in an enclosed state. During volume expansion, a working chamber continues to communicate with an opening called a suction port, allowing gas to be drawn in the working chamber from the outside for compression. After the working chamber reaches the position at which its volume is the maximum, the working chamber ends the communication with the suction port, thereby trapping the gas in the working chamber. The gas is then compressed as the working chamber reduces in volume. After the gas is compressed to a given pressure, the working chamber communicates with an opening called a delivery port and discharges the compressed gas therefrom until its volume becomes zero.